...that is strange; I routinely leave my charged (green) pack in the charger until I feel the need to switch it out with the one in the controller. Granted, it's more like a couple of months but I would assume it would simply stop charging once it reaches full capacity. If you can, grab a friends battery and try it in your charger. If it immediately goes from red to green, I'd chalk it up to a bad charger. Good luck.